Heavy Freezing Spray Warning 155, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 PM AKST TUE NOV 22 2011

.ANALYSIS AND UPPER LEVELS...
AN UNUSUALLY RARE EARLY SEASON COLD SNAP CONTINUES TODAY. OVER THE
PAST COUPLE DAYS THE POLAR VORTEX HAS DISPLACED SOUTH OVER ALASKA IN
THE FORM OF A DEEP UPPER LEVEL LOW. THE LOW ENCOMPASSES THE FULL
STATE OF ALASKA WITH CLOSED HEIGHT LINES EXTENDING FROM BARROW INTO
THE NORTHERN PACIFIC OCEAN. THE SYSTEM BRINGS AN OVERRUNNING FLOW
FROM THE SOUTHEAST THROUGH THE CENTRAL INTERIOR. THE ASSOCIATED SNOW
AND CLOUD COVER HAS HELPED MODERATE THE TEMPERATURES IN TERMS OF
KEEPING THE BITTER COLD AWAY. AT THE SURFACE A 970MB LOW RESIDES IN
THE GULF BUT NOT MUCH OF A SURFACE GRADIENT TO SPEAK OF.

.MODEL DISCUSSION...
GUIDANCE IS IN GOOD GENERAL AGREEMENT WITH THE UPPER LEVEL PATTERN.
MODEL CONSENSUS HAS THE POLAR LOW MOVING INTO THE GULF OF ALASKA AND
FILLING OVER THE REST OF THE WEEK. AT THE SAME TIME SEVERAL
DISTURBANCES WILL FORM ON THE BACKSIDE OF THE LOW MOVING SOUTH ALONG
THE WEST COAST. FURTHER OUT WEST A CLOSED LOW OVER KAMCHATKA WILL
JOIN THE CIRCULATION IN THE EAST IN THE FORM OF AN OPEN WAVE
PROPAGATING SOUTHWARD CROSSING THE ALEUTIANS. THE SURFACE PATTERN
DOES NOT SHOW ANY REFLECTION OF THE UPPER WAVES COMING FROM THE
NORTH. WITH THE TROUGH FULLY ENTRENCHED ACROSS ALASKA AND THE GULF
SEVERAL SURFACE LOWS WILL QUICKLY CROSS THE ALEUTIANS AND MOVE INTO
THE GULF OF ALASKA. FOR SUCH AN ANOMALOUS PATTERN THE MODELS SEEM TO
HAVE A GOOD HANDLE ON ITS EVOLUTION WHICH I BELIEVE TO BE FUNCTION OF
THE STABILITY OF THE REGIME.

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...THE BELOW NORMAL COLD CONTINUES FOR THE SHORT
TERM. THANKFULLY CLOUD COVER FROM THE GULF LOW WILL KEEP TEMPERATURES
FROM COMPLETELY FALLING OFF THE TABLE. AN EASTERLY WAVE ROTATING
AROUND THE UPPER LOW WILL BRING A CHANCE OF SNOW TO THE COPPER RIVER
BASIN...MATANUSKA VALLEY...AND ANCHORAGE BOWL OVERNIGHT INTO
WEDNESDAY MORNING. TOWARD LATE WEEK CLOUDS WILL DECREASE AND THE
COLD DRY PATTERN OF THE PREVIOUS WEEK WILL CONTINUE.

SOUTHWEST ALASKA...UNSEASONABLY COLD BREEZY PATTERN WILL PREVAIL
THROUGH THE DAY. WINDS SHOULD BEGIN TO COME DOWN FOR THE INTERIOR
TONIGHT INTO THURSDAY MORNING. EXPECT SNOW SHOWERS FOR THE AKPEN AND
EASTERN BRISTOL BAY ZONES. SCATTERED SNOW SHOWERS WILL CONTINUE FOR
THE AKPEN ON WEDNESDAY WITH PARTLY SUNNY CONDITIONS. COLDER AIR
MOVING SOUTH ACROSS THE BERING SEA/BRISTOL BAY REGION WILL KEEP
SCATTERED SNOW SHOWERS FOR THE REST OF THE WEEK WITH WINDY
CONDITIONS.

BERING SEA AND ALEUTIANS...SEVERAL WEAK FEATURES WILL KEEP
PRECIPITATION IN THE FORECAST FOR THE NEXT FEW DAYS. A WEAK FRONT
OVER THE CENTRAL/EASTERN ALEUTIANS WILL KEEP A CHANCE FOR SNOW IN
THE FORECAST AND A BROAD UPPER LEVEL TROUGH WILL KEEP A CHANCE FOR
MIXED PRECIPITATION FOR THE WESTERN ALEUTIANS. TOWARD THE END OF
THE WEEK COLD NORTHERLY FLOW OVER THE BERING/BRISTOL BAY AREA WILL
KEEP SNOW SHOWERS ACROSS THE AREA IN THE BRISK FLOW.

.LONG TERM FORECAST...
AT THE START OF THE WEEKEND A BROAD UPPER TROUGH WILL ENCOMPASS MOST
OF THE STATE KEEPING A BENIGN PATTERN IN PLACE. OUT WEST A CLOSED
LOW OVER KAMCHATKA WILL DRAG A FRONT OVER THE ALEUTIANS BRINGING A
PERIOD OF SNOW THEN RAIN TO START THE WEEKEND. THE FRONT WILL STALL
VERY CLOSE TO THE SOUTHWESTERN MAINLAND WITH A BROAD TROUGH OVER THE
BERING KEEPING SHOWERY PRECIPITATION AROUND THE AREA.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 171.
         WIND CHILL ADVISORY 131 145 155 161.
MARINE...STORM WARNING...150.
         GALE WARNING...127 130 132 138 155 160.
         HEAVY FREEZING SPRAY...126 127 130 132 138 150 160 180 185.
FIRE WEATHER...NONE

MTL NOV 11